Microwave ferrite devices having particular arrangements for the magnetizing source



H. SALTZMAN ET AL MICROWAVE FERR Nov. 28, 1967 3,355,680

ITE DEVICES HAVING PARTICULAR ARRANGEMENTS FOR THE MA'GNETIZING SOURCE Filed March 29, 1965 2 Sheets-Sheet l a W lwr/ E LE CTROMAGNET K T R C mm 0 D- 4 IU D5 2 6 4 4 4 2 1 ll- 2 3 J m A l. N F 4 mo N U 0 R a H M w d INVENTORS HAROLD SALTZMAN BY THOMAS F. VALLAR m v M411 ATTOR EYS NOV. 28, 1967 s T N ET AL 3,355,680

MICROWAVE FERRITE DEVICES HAVING PARTICULAR ARRANGEMENTS FOR THE MAGNETIZING SOURCE Flled March 29, 1965 2 Sheets-Sheet 2 M MATERIAL FIG 3 $3540 PLANE/ PERMANENT FERIKITE MAGNET 6B u T m. FERR'TE enoumo PLANEJSS 1' MAGNET MATERIAL GROUND PLANE 52 26 I 1 Fm WQQ 56 7 J PERMANENT mm WALL MAGNET FIG.-- 5

INVENTQRS HAROLD SALTZMAN THOMAS F. VALLAR Fwd/QM A TTORNEYS United States Patent 3,355,680 MICROWAVE FERRITE DEVICES HAVING PAR- TICULAR ARRANGEMENTS FOR THE MAG- NETIZING SOURCE Harold Saltzman, Woodland Hills, and Thomas F. Vallar, Burbank, Caliii, assiguors to E 8: M Laboratories, North Hollywood, Calif.

Filed Mar. 29, 1965, Ser. No. 443,250 13 Claims. (Cl. 333-1.1)

This invention relates to microwave devices, and more particularly to devices of the type utilizing magnetized ferrite elements for control of Wave propagation,

Microwave ferrite devices and systems have come into wide use because they make feasible completely electronic transmission and modification of microwave energy. They thus operate with high reliability and can operate where necessary at extremely high speeds. In addition, they often offer significant advantages in size, cost and weight over prior art devices for performing comparable functions. Typically, whether in waveguide or wave transmission lines, the ferrite is magnetized in a selected direction and with a chosen field strength to establish the desired wave interaction and achieve the needed energy absorption, phase shift, or wave diversion. The microwave ferrite devices now in use include isolators, phase shifters, limiters, variable attenuators and circulators, among others, and the present invention is applicable to all such devices.

Microwave ferrite circulators utilizing multiport symmetrical configurations provide particularly useful examples of the invention because they are small in size, light in weight and useful for a variety of purposes. They are accordingly being used in a substantial and growing number of applications. Such devices permit selective diversion of electromagnetic energy from any given port to the adjacent port in one direction of circulation, while also highly attenuating waves moving in the reverse direction of circulation. The circulator function may be used, alone or in combination with other devices, for any of a number of purposes in systems and subsystems. Energy from a transmitter may be directed in time varying fashion through a matrix of selectively actuated circulators to the radiating elements of a phased array antenna system. For such systems the circulators provide a compact, electronically controlled switching system. Circulators may also be used for isolation of a high-power transmitter, by diversion of reflected energy from a system into a load. In other instances, magnetically switched circulators are coupled into a given line, and actuated when it is desired to test, calibrate or sample wave transmission. In still other instances the circulator is used as a low-loss coupling line in transferring received energy from an antenna through a low-noise preamplifier into a receiver. Circulators also are used to perform typical radar duplexer functions.

Microwave ferrite circulators are typically based upon T or Y configurations, although they may be in other forms as well, and are often used in combinations to increase the number of ports available Perhaps the most common form at present is the three port Y device, using waveguide or strip transmission line and incorporating a vertically magnetized ferrite load or disk as the ferrimagnetic element at the central axis of the Y. In the strip transmission line version of this device, the ferrite is usually in the form of a pair of disks, one between the center conductor and each of the different ground planes. Magnetization of the ferrite in the direction perpendicular to the broad faces of the waveguide or strip line is typically provided by a permanent magnet or by an electromagnet, the electromagnet being used wherever it is de- 3.355158% Patented Nov. 28, 1967 sired to reverse the sense of magnetization and thus achieve a switching action.

The performance characteristics of circulators of this type must include a bandwidth characteristic suflicient to encompass the operating bandwidth of the associated system, while at the same time insertion loss and VSWR must be held to a minimum in the chosen direction of circulation. Furthermore, the isolation between ports in the undesired direction of circulation must be a maximum, and the device should be magnetically shielded and stray fields should be minimized.

Needed compactness and magnetic shielding are usually achieved at the sacrifice of weight or considerable loss of efficiency. The permanent magnets typically are C-shaped elements extending about the circulator on one side and engaging the opposite broad faces of the device, or disk shaped and located on each broad face at opposite ends of the ferrite outside the transmission line. Electromagnets are typically mounted external to the ferrite device with pole tips disposed adjacent to the opposite ends of the ferrite. The electromagnet coils are wound and energized so as to provide magnetization of the ferrite in either direction. These permanent magnets and electromagnet devices are not used together, and therefore cannot combine the advantages of the compactness, reliability and freedom from power requirements of the permanent magnet device with the switching capability of the electromagnet-controlled device.

It is therefore an object of the present invention to provide an improved microwave ferrite device having 'a compact and effective magnetic shielding structure, but minimum size and weight.

Another object of the present invention is to provide an improved waveguide or transmission line circulator of the symmetrical ferrite-loaded type.

Another object of the present invention is the pro: vision of an improved device for uniformly magnetizing a ferrite element in a waveguide or transmission line system in either direction.

Another object of the present invention is to provide an electronic switch for controlling the transmission of microwave energy from and to selected ports.

A further object of the present invention is to provide improved ferrite waveguide and transmission line systems, including coaxial and strip transmission lines, such devices being of extremely small size but having wide band electrical characteristics.

Yet another object of the present invention is to provide an improved electronically-controlled microwave switch having the property of operating in a selected direction in the event of a power failure.

These and other objects of the present invention are achieved by microwave ferrite devices in which a magnetizing source, in the form of a permanent magnet or an electromagnet, or both, is mounted adjacent to one end or side of the ferrite components, and a closed magnetic path which includes a part of the waveguide or transmission line system is provided to the opposite end or side of the ferrite. A uniform magnetic field in one direction, or of switchable direction, is established within the ferrite although the device is compact, light and completely magnetically shielded.

One form of improved circulator in accordance with the invention, provided as an example only, comprises a three port Y or T junction within a strip transmission 1 line device. Ferrite disks are positioned at the central axis of the Y, between the center conductor and the ground planes. A uniform magnetic field of either polarity and selected strength is established through the ferrite by a single permanent magnet and an electromagnet disposed in series fashion along the central axis and adjacent one end of the ferrite, and a thin ground plane of the transmission line. The opposite ground plane of the transmission line is formed entirely of a soft magnetic material, such as iron, and thus provides a magnetic return path to the opposite end of the ferrite which is joined to the magnetic source or sources by side and end walls of similar material. The permanent magnet may be in the form of a small disk engaging a pole piece which sets flush against the thin ground plane, and the core of the electromagnet may be disposed in direct contact with the permanent magnet.

Important further aspects of the invention reside in the dual use of two magnetic sources in this fashion. The permanent magnet has a field strength of H and the electromagnet has a field strength of 2H when energized. Thus this arrangement provides a ferrite circulator which is magnetically biased to provide circulation in one direction, but can be switched to provide circulation in the opposite direction. The circulator latches, or returns to a selected direction of circulation if power is lost or terminated. It should be appreciated that use of the magnetic elements in the ground plane do not disrupt the electromagnetic wave (RF) propagation, and that a symmetrical magnetic field exists within the ferrite elements, even though the magnetic path is asymmetrical. A small permanent magnet of high energy content and coercivity is employed, and when used in this manner does not tend to become demagnetized. In addition, the system remains completely magnetically shielded and stray field problems are minimized.

In accordance with another aspect of this invention the combined RF and magnetic paths are utilized in a permanent magnet type of circulator. Although a single permanent magnet is mounted on one side, the field is kept uniform by providing a magnetic ground plane for the transmission line on the opposite side, with an external return path extending from the permanent magnet to the magnetic ground plane.

In yet another type of device in accordance with the invention, a microwave ferrite circulator is provided in the form of a strip transmission line device having a per manent magnet symmetrically disposed at the intersection point of the arms of the center conductor, between two ferrite elements. The two ground planes of the circulator are both magnetic, and are interconnected by an external magnetic coupling to retain the characteristics of complete magnetic shielding, a low loss magnetic path, and a uniform field within the ferrite.

A better understanding of the invention may be had by reference to the following description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view, partially broken away, of a latching microwave ferrite circulator in accordance with the invention;

FIG. 2 is a plan view, partially broken away, of the arrangement of FIG. 1;

FIG. 3 is a side sectional view, taken along the lines 33 of FIG. 2, and showing further details of the arrangement of FIG. 1;

FIG. 4 is a perspective view, partially broken away, of a different form of symmetrical circulator in accordance with the invention, utilizing only a permanent magnet;

FIG. 5 is a side sectional view of the device of FIG. 4, showing further details thereof;

FIG. 6 is a perspective view, partially broken away, of yet another circulator device in accordance with the invention; and

FIG. 7 is a side sectional view of the arrangement of FIG. 6.

The symmetrical circulator device 10 shown in FIGS. 1-3 is an electronically switchable device which provides coupling between adjacent ports in either direction of circulation, but also operates in a latching manner. The device asshown is constructed. for use in a an mis ion line system operative in the range from 5.45.9 gc. Although a coaxial transmission line system is shown coupled to the various ports, it will be appreciated that strip transmission line and waveguide systems may be used in equivalent fashion where appropriate for the wavelength of the particular signal being propagated. Similarly, although the microwave ferrite devices shown are examples of strip transmission line circulators, it will be appreciated that the concepts of the invention can be applied to other ferrite devices as well as other wave transmission means. For example, the features of the switchable strip transmission line circulator to be described may be used to advantage in a controllable phase shifter in waveguide as well. Many other extensions and uses of the inventive aspects will present themselves to those skilled in the art, and it should expressly be understood that the present examples have been chosen for ease of understanding and are not to be construed as limiting the invention.

In the device of FIGS. 13, the inlet and outlet ports 12, 14, 16 designated 1, II and III for reference, are three coaxial connectors of conventional type positioned parallel to the same axis. The circulator region of the device It) is defined by a generally rectangular housing 26 and within this region the center conductors of the coaxial connectors are coupled in conventional fashion to the arms of the center conductor 22 of a symmetrical Y junction for a strip transmission line, as best seen in FIG. 2. Dielectric loading elements 2 4 are disposed along the arms of the Y, between the center conductor 22 and each of the adjacent ground planes. Two magnetized ferrite disks 26, 27, one on each side of the center conductor 22 at the central axis of the device, provide the substantially loss-less nonreciprocal wave diversion typical of such circulators.

The term ferrite is here used generally and descriptively to refer to any form of gyromagnetic element in a microwave transmission device. It will be appreciated that any ferromagnetic or ferrimagnetic element, including particularly the garnet materials, may be utilized, and that the term ferrite is used herein to apply to all such elements both for ease of reference and because of the prevalent use of the term.

One ground plane of the circulator consists of 2. rectangular iron member 34 which also provides a magnetic path. The opposite ground plane is a thin fiat conductive element 32 against which is seated a disk forming a magnetic pole piece 34. A permanent magnet 36 in the form of a fiat circular disk symmetrical with the central axis of the device engages the pole piece 34. The core 39 of an electromagnet 38, also symmetrical with the central axis of the device 10, engages the permanent magnet 36 on the opposite side from the thin-walled ground plane 32. The coil 40 of the electromagnet 38 encompasses the core 39, and the opposite end of the core 39 from the permanent magnet 36 is in engagement with a rectangular iron plate forming a bottom Wall 42 of the housing 20. Terminals 41 for the electromagnet 38 are connected to a suitable switching source (not shown). Iron side walls 44, 45 for the housing 20 complete a magnetic return path back to the magnetic ground plane 30 of the circulator. Suitable additional structural rigidity and electrical properties are provided through the use of end wall portions 47, 48 of conventional RF conductive material.

It will be observed that although the magnetic sources 36, 38 are asymmetrically placed relative to the ferrite disks 26, 2-7, the magnetic path is closed about the ferrite 26, 27 and a uniform magnetic field exists within the ferrite disks 26, 27. Assuming, as a first example, that the electromagnet 38 is not energized, the magnetic field is solely generated by the permanent magnet 36. The efiective reluctances of the thin-walled ground plane 30 and the center conductor are too low to present significant gaps in the magnetic path, and this in any event may be compensated for by increasing the strength of the permanent magnet 36. Therefore, from the opposite broad faces of the permanent magnet 36, the magnetic flux path is completely closed, extending through the pole piece 34, the thin-walled ground plane 32, one ferrite disk 27, the center conductor 22, the other ferrite disk 26, the magnetic ground plane 30, the side walls 44, 45 and the bottom wall 42 of the housing 20 to the opposite end of the core 39 of the electromagnet 38, and then to the permanent magnet 36.

With a permanent magnet 36 having a field strength H arranged in this manner and with a suitable direction of magnetization in the ferrite elements 26, 27, the circulation direction is [ell- 111, with high attenuation in the reverse directions. For circulation in the reverse direction (III- II I), however, the electromagnet 33 is energized with a strength 2H to provide a magnetic field of like strength and opposite polarity within the ferrite elements 26, 27. The number of ampere turns required, of course, is dependent upon the strength of the permanent magnet 36 as well as the remaining. parts of the magnetic path, and is determined by conventional techniques. It has been found that a commercially available permanent magnet having high energy content and coercivity material is suitable for avoiding tendencies toward demagnetization of the permanent magnet 36 under conditions of repeated opposite magnetization because of energization of the electromagnet 38. Additionally, this magnetic element may be extremely small and light.

Another important aspect of this arrangement resides in the fact that, for a selected normal direction of circulation, the device latches without power. Switching power is required only for the reverse direction of circulation, and fail-safe operation is assured because the circulator reverts unambiguously to the normal direction of circulation in the event of power failure or termination. The absence of moving parts and special driving circuit requirements assures high reliability and virtually indefinite life.

Suitable dimensions and materials for the ferrite and magnet of a circulator in the 5.45.9 gc. range have been found to be as follows:

Ferrite: Gl600 Garnet material, supplied by Transtech,

Inc.

Ferrite dimensions: 0.102" thick by 0.400 diameter Magnet dimensions: 0.425" diameter by 0.050" thick The body dimensions of the housing of this device are 1.5" long x 1.5 wide x 1.675" high, and the device weighs 6 ounces. Constructed in this manner for the frequency range indicated, electrical characteristics are found to be as follows.

Insertion loss: 0.3 db max. VSWR: 1.20 max. Isolation (crosstalk) 20 db min.

It will be noted that the RF transmission path within the circulator section is the same as in the devices of the prior art, except for the inclusion of one magnetic ground plane. Because this ground plane is also conductive, and because it is a relatively massive signal reference maintained at a common potential, there is no disruption of or attenuation in the conductive path.

A different arrangement in accordance with the invention, consisting of a fixed circulator device 50, is shown in FIGS. 4 and 5, to which reference is now made. As described in conjunction with the arrangement of FIGS. 1-3, the circulator region is defined by a transmission line device of Y-shape, with two ferrite disks 26, 27 disposed on opposite sides of the center conductor 22 at the central axis. One ground plane 52 of the circulator 59 comprises an iron, steel or other rectangular plate, whereas the other ground plane 54 comprises a thin-walled conductive strip. A disk-shaped magnetic pole piece 34 is positioned on the outer side of the thin-walled ground plane 54, and a permanent magnet 56 is positioned on the side of the pole piece 34 opposite the ground plane 54.

The magnetic path is completed by an end plate 57 and a side wall 58 extending in a closed magnetic circuit to the magnetic ground plane 52. Alternatively, the permanent magnet may be replaced by an electromagnet, if it is desired to perform a switching function without a latching action. Dielectric loading elements which may be used within the circulator region have not been shown for clarity of understanding.

The device of FIGS. 4 and 5 operates in the first mode previously described, establishing the desired uniform field strength within the ferrite elements 26, 27 at all times, although the magnetic source is asymmetri cally positioned relative to the ferrite elements 26, 27. The arrangement is particularly light and compact.

In a different example of a circulator device 60 in accordance with the invention, as shown in FIGS. 6 and 7, rectangular slabs of magnetic material are used for both ground planes 62, 63 of a strip transmission line. Ferrite disks 26, 27 are positioned between the ground planes 62, 63 and the center conductor 65 of the Y-shaped transmission line, and a magnetic side wall 67 completes the magnetic circuit between the ground planes 62, 63 and the ferrite disks 26, 2-7. The magnetic field is, however, generated by a centrally disposed permanent magnet 68 located within and conforming to an aperture in the center conductor 65 at the central axis.

While there have been described above and illustrated in the drawings various forms of ferrite microwave devices in accordance with the invention, it will be appreciated that the invention is not limited thereto, but includes all variations and alternatives falling within the scope of the appended claims.

What is claimed is:

1. A microwave ferrite device comprising wave transmission means having at least two parallel walls, ferrite means disposed within the wave transmission means along a selected axis normal to the parallel walls, permanent magnet means disposed adjacent to the ferrite means along the selected axis and at only on end thereof, the wave transmission means including a magnetic material wall member at the end of the ferrite means opposite from the permanent magnet means, and means providing a magnetic circuit path coupling the opposite end of the permanent magnet means from the ferrite means to the magnetic member of the wave transmission means, whereby the ferrite means is disposed in a complete magnetic circuit and magnetized in a direction along the selected axis.

2.. The invention as set forth in claim 1 above, wherein the permanent magnetic means is external to the wave transmission means and the means providing a magnetic circuit path is also external to the wave transmission means.

3. A microwave ferrite device for strip transmission line comprising the combination of a strip transmission line unit including a magnetic material ground plane section and a thin-walled electrically conductive ground plane section, ferrite means disposed along an axis normal to the ground plane sections between the magnetic material and thin-Walled sections and having ends adjacent said sections, a single permanent magnet positioned along the axis of the ferrite means on the opposite side of the thin-walled conductive ground plane section from the ferrite means and adjacent to the thin-walled conductive ground plane section, and magnetic means completing a magnetic circuit path between the magnetic material ground plane section of the strip transmission line and the permanent magnet, whereby said ferrite means is disposed in a complete circuit path.

4. A microwave ferrite device comprising the combination of wave transmission means, ferrite means disposed within the wave transmission means, permanent magnet means disposed adjacent the ferrite means and means, including electromagnet means, disposed to form a complete magnetic circuit with the permanent magnet means hrough the ferrite means, said permanent magnet means 1nd electromagnet means being asymmetrically disposed 7elative to said ferrite means.

5. A microwave ferrite device comprising: wave transnission means, ferrite means disposed within the wave :ransmission means, permanent magnet means disposed on one side of the wave transmission means adjacent the ferrite means, electromagnet means disposed adjacent the permanent magnet means and in magnetic series therewith, on the same side of the wave transmission means, and means magnetically coupled to the electromagnet means and providing a magnetic return path to the ferrite means at the opposite side from the permanent magnet means.

6. A microwave ferrite device comprising: wave transmission means inoluding an internal ferrite element; the wave transmission means including magnetic wail means on one side of the ferrite element; and magnetic means coupled to the wave transmission means and in magnetic circuit with the magnetic wall thereof, said magnetic means including permanent magnet means for applying a selected uniform magnetic field through the ferrite element, and electromagnet means in series with the permanent magnet means, for completely reversing the direction of the magnetic field through the ferrite element despite the presence of the permanent magnet means.

7. A microwave ferrite device comprising: strip trans mission line means including a magnetic ground plane, a center conductor and a second conductive ground plane, a pair of ferrite elements disposed along a given axis between the center conductor and the opposite ground planes, permanent magnet means disposed along the axis and adjacent the conductive ground plane, an electromagnet including a center core coupled to the permanent magnet and an external coil for magnetizing the core in a selected direction, end and side plate means of magnetic material forming a complete magnetic circuit from the core of the electromagnet at the end opposite the permanent magnet to the magnetic ground plane of the strip transmission line means, such that a complete magnetic circuit exists through the ferrite elements, the permanent magnet and the core of the electromagnet, and along the magnetic walls to the magnetic ground plane to establish a uniform magnetic field within the ferrite elements, and means coupled to the energizing coil of the electromagnet, for generating a magnetic field of twice the strength and of opposite polarity to the strength of the field generated by the permanent magnet, such that a uniform magnetic field of selected strength and either polarity may be established through the ferrite elements.

8. A switchable microwave circulator comprising a symmetrical multi-port junction having a central axis, ferrite means disposed within the junction at the central axis, permanent magnet means positioned adjacent a first end of the ferrite means and at the central axis, electromagnet means positioned adjacent the permanent magnet means at the central axis, and means providing a magnetic return path from the electromagnet means to the end of the ferrite means opposite said first end.

9. A switchable microwave circulator comprising a symmetrical multi-port junction having a pair of ground planes, one of which is of magnetic material, disposed about a central axis, ferrite means disposed within the junction between the ground planes at the central axis, permanent magnet means positioned adjacent one end of the ferrite means at the central axis on the side opposite the magnetic ground plane, the permanent magnet means providing a field strength in the ferrite means of a strength H electromagnet means positioned adjacent the permanent magnet means at the central axis, the electromagnet means being energizable to provide a field strength of ZH and of a polarity opposite to that provided by the permanent magnet means, and means providing a magnetic return path from the electromagnet means to the magnetic ground plane of the junction.

10. A microwave ferrite device for strip transmission lines comprising the combination of a strip transmission line unit including a center conductor and a pair of ground planes, at least one of which is of magnetic material, ferrite means disposed between the ground planes along an axis normal to the ground planes, a single disk-shaped permanent magnet positioned along the axis of the ferrite means and adjacent the ferrite means, and magnetic means magnetically coupled to said magnetic ground plane and completing a magnetic circuit path about the strip transmission line unit to spaced apart regions along the aXis of the said ferrite means, whereby said ferrite means is magnetized in a direction along the axis.

11. The invention as set forth in claim 10 above, wherein said strip transmission line has both ground planes of magnetic material, wherein the ferrite means comprises a pair of ferrite elements, each engaging a different ground plane, and wherein the permanent magnet means is disposed internally within the strip transmission line, between the ferrite elements.

12. A ferrite microwave device including the combination of wave transmission means, ferrite means positioned along a selected axis within the wave transmission means, said. ferrite means to be magnetized along said selected axis, a single disk-shaped permanent magnet disposed along the selected axis of the ferrite means within the wave transmission means, and magnetic means extending outside the Wave transmission means and completing a magnetic circuit path to opposite ends of said ferrite means along the selected axis to provide a magnetic field within the ferrite means lying along the selected axis.

13. A microwave ferrite circulator including a strip transmission line having a center conductor, a first ground plane segment of magnetic material lying normal to a selected axis and a second ground plane segment spaced apart from the first and lying normal to the selected axis, a pair of ferrite elements, each positioned between the center conductor of the strip transmission line and a different one of the ground plane segments at the selected axis, permanent magnet means disposed along the selected axis adjacent the second ground plane segment on the side opposite said ferrite elements, and a magnetic coupling element connecting the end of the permanent magnet means opposite the second ground plane segment to the first magnetic ground plane of the circulator by a path external to the strip transmission line, such that a uniform magnetic field extending along the selected axis is established within the ferrite elements by a single permanent magnet asymmetrically disposed along the' selected axis relative to the ferrite elements.

References Cited UNITED STATES PATENTS 2,994,841 8/1961 Zaleski 333-24.1 3,072,867 1/1963 Heithaus 333-24.2 3,085,212 4/1963 Clark et al 3331.1 3,185,941 5/1965 Freiberg 33324.1 3,212,028 10/1965 Wantuch 333-24.2 3,231,835 1/1966 Nielsen et al. 3331.1

ELI LIEBERMAN, Primary Examiner.

HERMAN KARL SAALBACH, Examiner.

P. L. GENSLER, Assistant Examiner. 

8. A SWITCHABLE MICROWAVE CIRCULATOR COMPRISING A SYMMETRICAL MULTI-PORT JUNCTION HAVING A CENTRAL AXIS, FERRITE MEANS DISPOSED WITHIN THE JUNCTION AT THE CENTRAL AXIS, PERMANENT MAGNET MEANS POSITIONED ADJACENT A FIRST END OF THE FERRITE MEANS AND AT THE CENTRAL AXIS, ELECTROMAGNET MEANS POSITIONED ADJACENT THE PERMANENT MAGNET MEANS AT THE CENTRAL AXIS, AND MEANS PROVIDING A MAGNETIC RETURN PATH FROM THE ELECTROMAGNET MEANS TO THE END OF THE FERRITE MEANS OPPOSITE SAID FIRST END.
 10. A MICROWAVE FERRITE DEVICE FOR STRIP TRANSMISSION LINES COMPRISING THE COMBINATION OF A STRIP TRANSMISSION LINE UNIT INCLUDING A CENTER CONDUCTOR AND A PAIR OF GROUND PLANES, AT LEAST ONE OF WHICH IS OF MAGNETIC MATERIAL, FERRITE MEANS DISPOSED BETWEEN THE GROUND PLANES ALONG AN AXIS NORMAL TO THE GROUND PLANES, A SINGLE DISK-SHAPED PERMANENT MAGNET POSITIONED ALONG THE AXIS OF THE FERRITE MEANS AND ADJACENT THE FERRITE MEANS, AND MAGNETIC MEANS MEGNETICALLY COUPLED TO SAID MAGNETIC GROUND PLANE AND COMPLETING A MAGNETIC CIRCUIT PATH ABOUT THE STRIP TRANSMISSION LINE UNIT TO SPACED APART REGIONS ALONG THE AXIS OF THE SAID FERRITE MEANS, WHEREBY SAID FERRITE MEANS IS MAGNETIZED IN A DIRECTION ALONG THE AXIS. 